🚀 go-pugleaf

For brevity I have resisted the use of reference material to support
my arguments.  If requested I will supply a complete list of source
material for the arguments presented below.

"R. Bailey" <bailer@rpi.edu> wrote:

>1. If there is no correlation between increased human exposure to UVR and 
>ozone depletion, is it because the depletion levels in inhabited 
>latitudes have not been large enough for this to be evident? 

1. There is some speculation about the actual levels of ozone
depletion at temperate latitudes, and how it arises.  The conservative
viewpoint is that it arises from the mixing of chemically perturbed
air from polar regions, whereas there is some evidence that some
depletion is due to linear (homogenous) processes.  The degree to
which the latter is involved is important in estimating on-going
trends.  At present the decrease in ozone levels over populated areas
would not exceed a few percentage points at maximum.

2. An important but often overlooked fact, is that a depletion of a
few points in ozone, does not translate directly into a proportional
increase in UVR.  This is due to variable weather and atmospheric
conditions, a small but significant amount of filtering of UV-B which
occurs below the depleted ozone ("self-healing"), and the fact that
ozone is already an incomplete filter for UV-B.  As a result there is
speculation whether ozone depletion results in an increase in surface
UV-B, and even if it does, this amount would be very small compared to
natural variations.  

3. Most importantly, any increase in UVR would be completely
overwhelmed by human behavioural patterns, in particular sun-wise
trends, and the use of "15+ blockout".  Also humans, like plants and
animals, are to varying degrees adapted to UVR.  It is reasonable to
expect that the latency in melanoma, and the protecting effect of
malanin, would produce a threshold exposure level, or hormesis effect
(I have no refs for this, but IMO it is self-evident).  This could
mean that even large increases in UVR would not be measured in
subsequent epidemiological studies, provided individuals maintain the
current "slip/slop/slap" techniques of sun protection.

> If so, 
>should we wait for the depletion to become large enough to show a 
>correlation before expressing active concern?

I have no objection to showing active concern, based on the
"precautionary principle".  What concerns me is that there has been an
over-reaction relative to the potential for significant environmental
damage, and considering that there are many other environmental issues
worthy of the "green dollar".  

The Montreal Protocol is unnecessarily expensive, due to the practice
of collecting and incinerating CFCs.  A little less panic might have
allowed for the release of CFCs into the atmosphere, along with a
phased introduction of replacement chemicals in line with the ability
of individual persons, companies, and nations to pay for the change in
infrastructure.  Also, IMO, an imbalance in the rate and nature of
introduction of CFC phase-out between developing and developed
countries has reduced the potential effectiveness of the MP.

>2. Or, are you maintaining that anthropogenic sources of ozone depleting 
>chemicals are negligible with respect to ongoing natural sources? 

I have never suggested such.  I have argued that ozone depletion from
natural sources exist, and are significant, but the effects are now
small relative to anthropogenic sources of Cl and Br.

>If so, 
>the science does not provide a comfortable support for this stand; 
>again, should we wait to see if current scientific understanding is 
>wrong?

I do not think the current scientific undertanding is wrong.  IMO the
public (and that includes many denizens of newsgroups) perception of
current scientific understanding is wrong.  

>3. Or, are you maintaining that no amount of ozone depleting chemicals 
>will have a significant effect? If so, how do you account for the known 
>chemical reactions?  

IMHO, looking at the matter logically, continued use of CFCs would
eventually result in increased UVR and measurable health effects, but
not for a very long time.  

Now, there are environmental issues in the world which result in
immediate, and devestating, environmental damage eg acid rain, soil
degradation, oil spills, forest and water resource mismanagement, etc
etc.  All of these issues are deserving of funds.  In a world where
half the human population are starving, I believe more care should be
taken in allocation of environmental protection resources.


...Greig